Work is in progress to establish that formylmethyl cobalamin is an intermediate in the enzymic conversion of ethyleneglycol to acetaldehyde. The point of attachment of propargyl-glycine, an irreversible inhibitor of cystathionase, to cystathionine synthetase is under investigation. The structure of the adduct found between HC triple bond C-CH2-N(CH3)2 and the flavin of mitochondrial amine oxidase is being investigated. The mechanism of action of the following irreversible inhibitors of plasma amine oxidase is under investigation: N triple bond C-CH2-NH plus 3; NH plus3-CH2-C(O)- phi; HC triple bond C-CH2NH plus 3.